Outdoor sunbathing and indoor tanning saloons, outdoor employment such as construction and farming and various forms of indoor employment like arc welding expose the surfaces of the skin to high levels of ultraviolet light. Such exposure may be dangerous. As reported by the American Cancer Society, there is a definite correlation between over-exposure to sunlight (solar ultraviolet light), or man made sources of ultraviolet light, and skin cancer. In this regard, the American Cancer Society recommends maximum cumulative exposure limits for specified periods, such as a week or month. Therefore, it is prudent to guard against cancer-producing over-exposure.
Existing techniques for determining exposure to ultraviolet light have suffered from a common drawback. They do not enable measurement of cumulative exposure to ultraviolet light over a series of episodes. Instead, existing techniques have included sunscreen ointments applied to the exposed skin to inhibit or reduce greatly the passage of ultraviolet light to the skin. Such techniques have also included electrical and electronic alarming devices for providing indications when a predetermine exposure level has been reached during any one continuous exposure time.
Thus, existing techniques do not enable individuals to monitor the cumulative amount of ultraviolet exposure received in a number of episodes. Although exposure may be limited to a safe level at any one sitting, the danger of cumulative overexposure remains ever present.
Consequently, it is desirable to have a new and improved device for monitoring the cumulative total amount of exposure to ultraviolet light, starting from any desired time, from repeated individual exposure episodes. The device should be inexpensively manufacturable, require little skill to use, and provide a convenient indication of accumulated exposure in a readily discernible manner.